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  1. #1

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    The X-I Frame - Something a little different

    Edit: It's alive! Photos and video further down



    So I am new to multirotors, but have been browsing the forums and reading everything I can for a while now. I have decided that I want to jump in to building one, and I want one stout enough that I can haul a go-pro camera now, and possibly upgrade to full FPV later. I was originally going to go with a bought frame, but being an industrial designer and mechanical engineer by career, with a full prototype shop at work, I decided that designing and building my own would be more fun/rewarding, and tailor it exactly to my needs.
    I started thinking about the basic H or X frames, but the H frames worried me with their tendency to twist flex and transmit vibrations, and the X frames had the problem of the props being visible in the video.
    So I had the idea to combine a simple X frame with a separate lightweight center frame (the I in the X-I name) to move the camera forward and the battery backwards, and to have that whole frame be heavily isolated from the motor booms for vibration resistance.
    Theoretically, by mounting everything heavy and sensitive to a single frame structure, and then isolating that from the main motor/boom structure, it should provide extra vibration damping, while still being light weight and stiff.
    That's the theory at least, so here are the pictures.
    The main boom arms are home depot towel bars, while the plates making up the rest of the frame are 1/8in polycarbonate sheet, to be upgraded later to G-10 or CF. The rest of the hardware are off the shelf standoffs screws and washers from Mc-Master Carr (or the supply room at work)
    The go-pro and battery are hung below the main frame, keeping the weight on the dampened section to help absorb any vibration that makes it through the rubber washers.
    The feet are splayed outward to help protect the props in a crash
    The main "I" frame is connected to the X frame solely just below the center of the X, while the rest of the frame does not contact.
    In this cross section you can see how the X frame plates are attached to the I frame with a set of rubber washer shock absorbers. The amount of rubber will have to be tuned to give good rigidity while absorbing vibrations.
    The motor to motor diagonal is 550mm, and according to my solidworks calculations, the frame should be around the 400g mark, with an AUW of around 1500g. Coming from the RC car world, and being a designer, I am also planning on designing and vacuum forming a lightweight lexan body shell, to protect the electronics, improve aerodynamics, and most of all, because it will look cool. That will come once I finalize the frame design. Should add very little weight, it will be very thin.
    So that is my work in progress design. Currently all the cut pieces fit on a single 1'x2' sheet, so costs should be low.
    The components I am planning to use so far are these:
    Hextronic DT750s
    http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=6247
    Turnigy Plush 25 amps (30s are out of stock)
    http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=2163
    Hobbyking KK2.0 LCD board
    http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=24723
    Slow fly 11x4.7 props (just linking one here, know I need 4 different ones)
    http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idproduct=22452
    Various wires and connectors, USB programmer, Turnigy 9x, ect.
    So, this is meant to be a combination build thread and discussion/critique, so I ask you, does this look like a good plan? Are my component choices ideal for what I am trying to do here? Is that combination of motor/prop going to work for me? What am I missing? Am I crazy and should go with something typical?
    Like I said, I am new to this, so I need all the advice you guys can give me, thanks for the help!

  2. #2

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    RE: The X-I Frame - Something a little different

    Update!

    I have finalized the CAD design, and we have started cutting the prototype.  Made some tweaks to the size and shape, added more details, and strengthened the main X frame.  Here are some pics of the final design:


    I have ordered all the parts, and have begun cutting parts on the CNC mill here at work.


    I'll keep this updated as I go!


  3. #3

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    RE: The X-I Frame - Something a little different

    So! The chips are beginning to fly on your project? Looking good. Curious? What did you settle on for material? CF or G10?

    I am so new to quads - heli's of any type for that matter. I have an entry level HeliMax quad just to see how adaptable I am to this new aspect of the rc hobby. But, in another life I did build my own rc drag racing chassis and settled into G10F4 over CF, as it proved much more survivable in a crash.

    Keep the updates coming, Thothtp. Anxious to see the quad finished and beating the air mercilessily with it's four rotors. [8D]

    Arnie
    arnie hauswald racing 1943
    r/c electric drag racing

  4. #4

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    RE: The X-I Frame - Something a little different

    For the first prototype I am using Polycarbonate sheet, should be plenty strong and very inexpensive, about $20 instead of $100 for CF. I will probably end up with G-10 on future cuts, but I wanted to start simple since I am sure there will be tweaks to make.

    Machining finished last night, time to pull it off the mill!

  5. #5

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    RE: The X-I Frame - Something a little different

    Parts are together and the frame is built!  Hit my weight target, and it came out even better then I expected.

    Here is the main frame put together for the first time

    Here I am showing the hand release folding mechanism.  It uses spring pins similar to an umbrella or EZ-UP, which lock the frame arms in place but allow you to fold it up in seconds without tools.  I was worried about rigidity here, but it looks to be rock solid.

    Looking at the bottom with the arm frame in place, you can see the vibration isolating grommets.

    The X frame with the motor mounts is entirely isolated from the main frame housing the electronics.  These grommets completely surround the hard parts so that there are no plastic or metal parts touching, only rubber.

    Forgive the mess here, this is our silicone soft tooling mold room, only place I could find an accurate scale.  The full frame with all hardware comes out to 1.15 pounds, or 521 grams.  Keep in mind this is using quite heavy (but very very cheap) 3mm (1/8in) polycarbonate sheet and aluminum arms - If made with carbon or G-10 that weight would drop a ton.  I was trying to keep it under 600g, and with all the features it has I am very happy with the result.

    And finally some pictures of the complete frame




    and finally, a video!
    [YOUTUBE]http://youtu.be/K7weSLrkWR0[/YOUTUBE]

    I'll keep this updated as I get started on the electronics, still waiting on the order to make it across on the slow boat from China :-(

  6. #6
    KRASHKOPTER's Avatar
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    RE: The X-I Frame - Something a little different

    Looks very nice so far. In fact, looks better than a lot of *brand* name quad setups. Keep up the good work and keep track of expenses...it may be a hit if you can give an attractive price (and if yer up to mass producing to sell them..lol)
    Thanks for posting.

    KRASH
    MCPX, MQX, KDS-450C, HK-500GT, DX7S

  7. #7

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    RE: The X-I Frame - Something a little different

    Its alive! Got everything wired up and functioning, and it has flown! Still working on getting all the tuning done, and still need to balance the props, but it is working great so far. The frame has plenty of room for everything, is very stiff and rigid, the folding works great, and even with out of balance props the vibrations are sucked right out of it. Very happy so far!
    I ended up adding crezzee's Super Simple Gimbal (http://www.rcgroups.com/forums/showthread.php?t=1793759) to auto balance the go pro, and it works great! Here is a video!
    Once I get it tuned and balanced (and learn to fly it, heh) I will update this with some on board flight videos. Here are the photos
    Here it is folded up, no tools, just click and lock.
    I'm already starting to look at FPV, have room for a flight camera below the go-pro, with a transmitter on the back. I do a lot of design and engineering work for Vuzix corporation, and showed the owner what I had built, he wants to give me some goggles to experiment with.
    Trying to figure out a decent inexpensive setup to get started with. Not looking for super long range, just something I can use to fly around within 500m or so. Its a big quad copter, I don't see myself going very far with it anyways. I was thinking about picking up a 200mw setup from hobbyking in either 900mhz or 5.8ghz, would that work for me or are they just too crappy? My radio is a Turnigy 9x that I am very happy with so far, but do I need to upgrade to a FrSky module? If the HK one doesn't work, are there any better options within the same price ballpark?
    Thanks again everyone!

  8. #8

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    RE: The X-I Frame - Something a little different

    Took it up with the camera today, and was reasonably successful. I haven't done any prop balancing yet, so the video is pretty shaky, and I think the gimbal may be a little too soft, but it flys great! I have almost no experience with flying anything really, so I am trying to learn the ropes and getting bolder each time I take it up.
    I also decided to crash test the frame by hitting a tree... on purpose of course! I didn't lose depth perception and accidentally back in to the tree that I thought I was still clear of...
    It passed the test with flying colors, after a 30 foot fall it broke a couple props and the frame collapsed like it was supposed to, no damage.
    Hopefully I can work out the jello and learn some skills and then I will be good to go!
    [youtube]https://www.youtube.com/watch?v=2ywjqZro0FM[/youtube]
    Here are some images as well, shows my front yard after the big east coast snowstorm.


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